1. Field of the Invention
The field of this invention relates to glass filled polyamide-imide phthalamide copolymers prepared in an organic solvent and to molding powders and molded articles prepared therefrom. More particularly, the field of this invention relates to glass filled polyamide-imide isophthalamide.
2. Background
Amide-imide polymers are a relatively new class of organic compounds known for their solubility in nitrogen-containing organic solvents when in the largely polyamide form. The major application of the amide-imde polymers has been as wire enamels. This is illustrated in U.S. Pat. Nos. 3,661,832 (1972), 3,494,890 (1970) and 3,347,828 (1967).
Compositions prepared from isophthalic acid and diamines and aliphatic diamines have found application in coatings and films. The prior art on this is summarized in U.S. Pat. No. 3,444,183 (1969).
Reinforced polyhexamethylene isophthalamides have been used to produce articles as disclosed in U.S. Pat. No. 4,118,364 (1978). However, the physical properties of these reinforced polyhexamethylene isophthalamides are insufficient for use in engineering plastics since their tensile strength and the continuous service temperature do not meet those required for engineering plastics.
The general object of this invention is to provide amide-imide and polyamide copolymers. A more specific object of this invention is to provide amide-imide and polyamide copolymers reinforced with glass fibers, glass beads or a mixture thereof. A more specific object of this invention is to provide polyamide-imide and amide polymers prepared from aromatic diamines and mixtures of an acyl halide derivative of an aromatic tricarboxylic acid anhydride and acyl halide derivatives of aromatic dicarboxylic acids wherein said polymers contain from 30 to 60 weight percent glass fibers, glass beads or mixtures of these. Another object is to provide glass-filled polyamide-imide and polyamide copolymers suitable for use as an engineering plastic particularly for use in the manufacture of valve plates. Other objects appear hereinafter.
I have now found that the novel amide-imide amide copolymers can be obtained by reacting acyl halide derivatives of benzene tricarboxylic acid anhydrides and acyl halide derivatives of aromatic dicarboxylic acids with aromatic diamines. I have also discovered that these polymers can be filled from about 30 to 60 weight percent with glass fibers, glass beads or a mixture thereof. Suitably, the aforementioned molding composition may contain from about 30 to 50 weight percent of glass fibers, glass beads or a mixture thereof.
Our studies have shown that fully aromatic amide-imide polymers are very expensive and need special injection molding equipment capable of withstanding injection molding temperatures in the range of 600.degree. to 700.degree. F. at the molding pressure in excess of 20,000 pounds per square inch. Our novel amide-imide amide copolymer and glass filled copolymers are much more economical than conventional polyamide-imide copolymers disclosed in U.S. Pat. Nos. 4,016,140 (1977) and 3,573,260 (1971) and yet retain the same thermal and mechanical properties of the copolymers disclosed in the aforementioned patents. This is a significant advance in the art and is wholly unexpected.
The use of polyamide-imide polymers as engineering plastics has been limited only by their relatively high cost. Thus, when the inherent cost can be brought down, the commercial application of these polymers will be greatly expanded. The copolymers of this invention have large cost advantages over the prior art compositions and thus promise to expand the commercial applications of these polymers.
The copolymers of this invention are prepared by reacting a mixture of an acyl halide derivative of an aromatic tricarboxylic acid anhydride and acyl halide derivatives of aromatic dicarboxylic acids with aromatic diamines.
The novel injection moldable copolymers of this invention comprise recurring polyamide A units of ##STR1## which are capable of undergoing imidization and polyamide B units of ##STR2## wherein the molar ratio of A units to B units is about 80 to 20 to 20 to 80, preferably 1 to 1 and wherein R is a divalent aromatic hydrocarbon radical of from about 6 to about 20 carbon atoms or two divalent hydrocarbons joined directly or by stable linkages selected from the group consisting of --O--, methylene, --CO--, --SO.sub.2 --, and wherein X is a divalent aromatic radical and.fwdarw.denotes isomerization.
In the injection molded form the polyamide A units have converted to the polyamide-imide A' units and the copolymer comprises of recurring polyamide-imide A' units of ##STR3## and polyamide B units of ##STR4## wherein the molar ratio of A' to B units is about 80 to 20 to 20 to 80 preferably 1 to 1 and wherein R and X are defined as above.
The copolymers of this invention are prepared from acyl halide derivatives of dicarboxylic acid such as isophthalic acid or terephthalic acid and an anhydride containing substance and aromatic diamines. Useful acyl halide derivatives of dicarboxylic acid include ##STR5## and related compounds. Suitably, the anhydride containing substance is an acyl halide derivative of the acid anhydride having a single benzene or lower acyl substituted benzene ring. The preferred anhydride is four acid chloride is trimellitic anhydride (4 TMAC).
Useful aromatic diamines include para- and meta-phenylenediamine, oxybis (aniline), thiobis (aniline), sulfonylbis (aniline), diaminobenzophenone, methylenebis (aniline), benzidine, 1,5-diaminonaphthalene, oxybis (2-methylaniline), thiobis (2-methylaniline), and the like. Examples of other useful aromatic primary diamines are set out in U.S. Pat. No. 3,494,890 (1970) and U.S. Pat. No. 4,016,140 (1977) both incorporated herein by reference. The preferred diamine is meta-phenylenediamine.
I have found that the polyamide-imide amide copolymers are improved by the addition of reinforcing material particularly the mechanical properties of the copolymers are improved is these copolymers contain from 30 to 60 percent by weight glass fibers, glass beads or a mixture thereof. In the preferred range the copolymers contain 30 to 40 percent by weight of the glass reinforcing material, glass fibers, glass beads or a mixture thereof. Suitable reinforcing materials can be glass fibers, glass beads, glass spheres, glass fabric. The glass fibers are made of alkali-free boron-silicate glass (E-glass) or alkali-containing C-glass. The thickness of the fibers is preferably on average between 3 um and 30 um. It is possible to use both long fibers with an average length of from 5 to 50 mm and also short fibers with an average filament length of from 0.05 to 5 mm. In principle, any standard commercial-grade fibers, especially glass fibers, may be used. Glass beads ranging from 5 um to 50 um in diameter may also be used as reinforcing material.
The reinforced polyamide-imide amide copolymers may be prepared in various ways. For example, so-called rovings, endless glass fiber strands, are coated with the polyamide melt and subsequently granulated. The cut fibers or the glass beads may also be mixed with granulated polyamide and the resulting mixture melted in a conventional extruder, or alternatively the fibers may be directly introduced into the polyamide melt through a suitable inlet in the extruder.
Injection molding of the novel glass filled polymer is accomplished by injecting the copolymer into a mold maintained at a temperature of about 300.degree. to 450.degree. F. In this process a 25 to 28 second cycle is used with a barrel temperature of about 600.degree. to 650.degree. F. The injection molding conditions are given in Table I.
TABLE I ______________________________________ Mold Temperature 350 to 450.degree. F. Injection Pressure 15,000 to 19,000 psi and held for 1 to 3 seconds Back pressure 100 to 220 psi Cycle Time 25 to 28 seconds Extruder: Nozzle Temperature 600.degree. F. to 630.degree. F. Barrels: Front heated to 600.degree. F. to 630.degree. F. Screw: 20 to 25 revo- lutions/minute ______________________________________
The mechanical properties of the polymers prepared in the Examples are given in Tables 2, 3, and 4 and show that these polymers have excellent mechanical and thermal properties.
In a preferred embodiment 1 mole meta-phenylenediamine is dissolved in a nitrogen containing solvent such as dimethylacetamide or N-methylpyrolidone. A mixture of the 4 acid chloride of trimellitic anhydride and the acid chloride form of isophthalic acid in a molar ratio of 1 to 1 is added to the diamine solution over two hours at about 25.degree.-35.degree. C. The isophthalic anhydride and the 4 acid chloride of trimellitic anhydride may be either dry blended or molten. The viscous solution is then heated at about 50.degree. C. for one hour and the polymer is recovered by precipitation into water. The product is washed thoroughly and dried to a solids content in excess of 96%. The polymer is then dry blended with glass fiber, pelletized and injection molded under molding conditions as set forth in Table I. The mechanical properties of the copolymer are given in Tables 2, 3, and 4.